I plan to investigate the membrane-associated assembly of the filamentous phages, a group of viruses that infect cells carrying the F fertility factor. My initial approach has two parts: development of simple assays for the stages of virus assembly, and construction and isolation of viral and host-cell mutants that affect the assembly process, so that the specific step affected can be identified with the stage-specific assays. This work should result in a much clearer picture of the components involved in assembly, and set the stage for a deeper study of the process in vitro. If it turns out to be feasible to assemble infectious viruses from naked DNA in vitro, this might be the basis of a system for cloning very large pieces of foreign DNA. I also plan to study other ways in which knowledge of filamentous phage physiology might be expoited to devise new ways of manipulating and analyzing cloned DNA.